Cephalosporin antibiotics are markedly effective drugs for the treatment of infectious diseases in mammals in view of their excellent antibacterial activities and low toxicity against mammals. In recent years, a number of cephalosporin derivatives having an aminothiazolylacetyl group at the 7-position of the cephem ring have been studied and developed since they show strong antibacterial activities and high stability against .beta.-lactamase.
In various countries, many studies have addressed so-called "onium salt type cephalosporin antibiotics" such as ceftazidime and cefpirome which have an aminothiazolylacetyl group and a quaternary salt type substituent group at the 7-position and the 3-position, respectively and exert strong antibacterial activities and broad antibacterial spectrum ranging from gram-positive bacteria to Pseudomonas aeruginosa. However, these onium salt type cephalosporin antibiotics including ceftazidime and cefpirome are still unsatisfactory in terms of their antibacterial activities upon Pseudomonas aeruginosa and gram-positive bacteria including Staphylococcus aureus which have recently been given attention in a clinical viewpoint. Thus, great concern has been directed toward the development of novel cephalosporin antibiotics having improved antibacterial activities upon these bacteria.